Tool post including a spindle for a plurality of tool holders and a numerically controlled machine tool having such a tool post

Abstract

To shorten the time for the tool acceleration and deceleration phases.SOLUTION: A tool post (10) including a body (11) extending according to an axis A-A, the latter including, at one of its ends, a base (12) for fastening to a numerically-controlled machine tool and, at the other end, a head (13) movable in rotation, the head (13) including at least two tool-holder spindles (14, 14', 14"), each being intended to receive a cutting tool (15, 15', 15") in engagement, the spindles occupying, depending on the angular position of the head (13), a working position in which they are intended to carry out a machining operation on a workpiece held in position in a fitting position, or a standby position in which they are withdrawn from the workpiece, each of the spindles being configured to be controlled independently of the other in order to immobilize or drive in rotation the cutting tool carried thereby, irrespective of the position it occupies.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of numerically controlled machine tools for machining parts, preferably micromechanical parts, and to the field of equipment for such machines.

[0002] More particularly, the present invention relates to a tool post including a spindle for a plurality of tool holders, and to a numerically controlled machine tool having such a tool post. [Background technology]

[0003] Numerically controlled machine tools are intended, inter alia, for producing mass-produced parts by performing machining operations according to the instructions of a computer program. Such machines typically have tools mounted in a tool holder spindle and include a tool changer for changing the tools held in the tool holder spindle, the tool changer adapted to the machining operation to be performed on a part held in place on a fixture.

[0004] When changing tools, the machine tool loses productivity in the sense that the machining operation is interrupted. Therefore, the goal is to minimize the tool change time. To that end, tool changers have been developed to perform as much work as possible in the mask time, minimizing machine downtime and increasing productivity.

[0005] For example, a multi-spindle tool post is known that has a head in which several tool holder spindles are arranged, and one of the tool holder spindles is in operation while the others are stationary. In particular, the operating tool holder spindle is engaged with the drive mechanism by a coupling system. Therefore, between two machining operations, the tool can be changed by disengaging the operating tool holder spindle, i.e., the spindle holding the tool that needs to be changed, rotating the head so that the next tool holder spindle appears, and connecting this tool holder spindle to the drive mechanism.

[0006] However, this solution is not entirely satisfactory in that, although the tool change time is reduced, it is not completely masked. In fact, with this type of multi-spindle tool post, between tool changes, the tool to be changed must be decelerated before the tool change, and then the next tool must be coupled to the drive mechanism and accelerated to the machining rotation speed. Such multi-spindle tool posts also require a certain amount of time to remove the tool to be changed, rotate the head, index the next tool, align it with the coupling system, and then couple it. Furthermore, this solution is particularly complex and expensive due to the coupling system.

[0007] Multi-spindle tool posts address the issue of tool holder spindle acceleration and deceleration, but in these tool posts, all tools are driven to rotate simultaneously. Therefore, when a tool is replaced, the next tool is already driven at machining speed and ready to begin machining the part. However, such multi-spindle tool posts require a significant amount of energy to rotate all the tools simultaneously. Furthermore, the maximum rotational speed of the tools held by them is relatively limited by the kinematic chain of motion transmission.

[0008] Taken together, whether the tools held in the tool post are rotated individually or simultaneously, the bulkiness of prior art multi-spindle tool posts creates a high moment of inertia and increases the risk of collision between the mounting member and the tools held in the tool post.

[0009] In addition to the aforementioned drawbacks, these solutions are not suitable for machining micromechanical parts. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention solves the aforementioned drawbacks by providing a solution that allows to completely mask the tool change time, in particular by masking the acceleration and deceleration phases of the tool. Another object achieved by the present invention is to maximize the compactness of the machine tool and reduce the moving mass. [Means for solving the problem]

[0011] To that end, the present invention relates to a tool rest having a body extending along an axis AA, one end of which has a base for fastening to a numerically controlled machine tool, and a rotatable head at the other end. The head has at least two tool holder spindles, each intended to engage and receive a cutting tool. Depending on the angular position of the head, the spindles occupy either a working position intended to perform a machining operation on a workpiece held in a fixed position on a mounting member, or a standby position remote from the workpiece. Each of the spindles is configured to be controlled independently of the other spindles in order to stop or rotate the cutting tool held therein, regardless of the position it occupies.

[0012] Because the spindle is independently servo-controlled, it is possible to accelerate and decelerate the spindle in a masked time. Therefore, this invention allows tool changes to be performed while reducing the wait time until the next tool contacts the workpiece to just the head rotation time. Due to the features of this invention, tool change times between chips are estimated to be in the range of a few tenths of a second.

[0013] The present invention also has the advantage that it can be adapted to any existing machine tool.

[0014] The present invention also allows the spindle to reach relatively high rotational speeds, for example, 60,000 to 80,000 revolutions per minute.

[0015] In particular embodiments, the invention may further include one or more of the following features, considered individually or in any technically feasible combination:

[0016] In a particular embodiment, the axis of rotation of the head coincides with axis AA.

[0017] In certain embodiments, the base is configured so that axis AA forms an angle of 35 to 55 degrees with respect to the vertical axis.

[0018] These features are related to maximizing the compactness of the device.

[0019] In certain embodiments, the major axes are preferably evenly distributed around the axis of rotation of the head, and each major axis is arranged such that the axes BB, BB' and BB" form an angle of 35 to 55 degrees with the axis AA, and such that the axes BB, BB' and BB" do not intersect.

[0020] On the one hand, this feature makes it easier to remove the tool when it is at rest to avoid or limit the risk of collision with the mounting parts, and on the other hand, it makes it possible for all spindles to maintain the same working position, thereby ensuring that machining tolerances can be met.

[0021] In certain embodiments, the major axes are arranged relative to one another such that projection of the longitudinal axes BB, BB' and BB" onto a plane P perpendicular to the axis AA forms a regular polygon of degree n centered on the axis AA, where n is the number of major axes.

[0022] In certain embodiments, the main shafts are disposed such that the longitudinal axes BB, BB' and BB'' are spaced from the axis AA by a distance greater than the radius of the main shafts.

[0023] This feature also relates to removing the tool when it is at rest to avoid or limit the risk of collision with the attachment.

[0024] In certain embodiments, each of the spindles has its own motor for rotating or stopping the cutting tool held therein.

[0025] This feature allows for a reduction in energy consumption of the tool post, since the spindles that are not performing machining operations stop rotating about their corresponding longitudinal axes.

[0026] In certain embodiments, at least one spindle is adapted to occupy at least two different working positions, each working position being determined by a predetermined angular position of the tool post head.

[0027] In certain embodiments, the at least one spindle is adapted to continuously occupy the working position as the tool post head rotates, an arrangement that also includes continuous movement of the mounting member.

[0028] According to another object, the invention relates to a numerically controlled machine tool, preferably for machining micromechanical parts, comprising at least one tool post as described above, fixed by its base to a frame or directly to a carriage translatable in a vertical plane, whereby the axis AA forms an angle of 35 to 55 degrees with the vertical axis, said machine tool further comprising a mounting member intended to hold the part to be machined in a fixed position.

[0029] In a particular embodiment, the machine tool has two tool posts disposed on opposite sides of the mounting member.

[0030] In a particular embodiment, the machine tool has a protective wall against flying chips and cutting fluid, the body of the or each tool post being fluid-tightly engaged in a corresponding opening in said protective wall.

[0031] A further aspect of the present invention is a method of changing a tool in a machine tool as described above, comprising the steps of: a first cutting tool engaged with the spindle in the working position is intended to perform a first machining step, and a second cutting tool engaged with the spindle in the waiting position is intended to perform a second machining step and is prevented from rotating; - before the end of the first machining phase, the second cutting tool rotates about the B-B' axis until it reaches a rotational speed characteristic of the second machining phase; - upon completion of the first machining stage, the head rotates about axis AA to drive the spindle holding the second cutting tool to a working position so that the second cutting tool can begin the second machining stage, and to drive the spindle holding the first cutting tool to a standby position, the first cutting tool being prevented from rotating when the spindle holding the first cutting tool reaches the standby position.

[0032] Other characteristics and advantages of the invention will become apparent from a reading of the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a perspective view of a multi-spindle tool post according to a preferred embodiment of the present invention; [Figure 2] 2 is a view of the tool post of FIG. 1 oriented along the longitudinal axis of the tool post body. [Figure 3] FIG. 2 is a side view of the tool rest of FIG. [Figure 4] FIG. 2 is a perspective view of two tool rests disposed on either side of a workpiece mounting member. DETAILED DESCRIPTION OF THE INVENTION

[0034] Please note that the drawings are not drawn to scale for clarity.

[0035] FIG. 1 shows a tool rest 10 intended for machining components, preferably micromechanical components. In this embodiment of the invention, the tool rest 10 has a body 11 extending along a longitudinal axis designated "AA axis." One end of the body has a base 12 for fastening to a numerically controlled machine tool 20, and the other end has a head 13 rotatable about an axis coinciding with the AA axis. The head 13 has at least two tool holder spindles 14, 14', or 14", each intended to engage and receive a cutting tool 15, 15', or 15". Depending on the angular position of the head 13, each spindle 14, 14', or 14" occupies either a working position intended to perform a machining operation on a workpiece held in a fixed position on a mounting member 21, or a standby position spaced apart from the workpiece.

[0036] It should be noted that the tool post 10 can be driven in translation, for example, if the base 12 is fixed to a carriage (not shown) of a machine tool 20 that is movable along at least one translational degree of freedom relative to the XYZ trihedron, and preferably three degrees of translational freedom.

[0037] Alternatively, for example, if the base 12 is fixed directly to the frame 22 of the machine tool 20, the tool post 10 can be stopped.

[0038] Advantageously, spindles 14, 14' and 14" are configured to be controlled independently of one another to rotate or stop a cutting tool 15, 15' or 15" held therein. This feature is particularly advantageous when changing tools. Preferably, spindles 14, 14' and 14" are powered spindles, also known as "electronic spindles", each having its own motor to rotate or stop a cutting tool 15, 15' or 15" held therein.

[0039] In particular, in order to exchange the first cutting tool 15, which performs the first machining step, for a second cutting tool 15' intended to perform the second machining step, the second cutting tool is rotated before the end of the first machining step until it reaches a rotational speed characteristic of the second machining step.

[0040] The first cutting tool 15 is engaged with the spindle 14 in the working position, and the second cutting tool 15' is engaged with the spindle 14' in the standby position.

[0041] When the first machining stage is completed, the head 13 moves the spindle 14, which was in the working position, to the standby position and rotates the spindle 14', which was in the standby position, to the working position. The second cutting tool 15' has already reached the machining rotation speed when the engaged spindle 14' was in the standby position, so the subsequent second machining stage begins immediately. At this time, the spindle 14 gripping the first cutting tool 15 is in the standby position and the first cutting tool is stopped.

[0042] Thus, when the second cutting tool 15' rotates and the first cutting tool 15 is stopped at mask time, the cutting tools are changed with reduced waiting time only while the head is rotating.

[0043] Each spindle 14, 14' and 14" extends along a longitudinal axis, designated "BB axis", "B-B' axis" and "BB" axis", respectively, which also forms the axis of rotation and which is shown in Figures 1 and 3 only for the spindle 14 in its working position. As shown in these figures, in its working position the spindle 14 is oriented so that its axis BB is parallel to a vertical axis. However, in another working position the spindle 14 can also be oriented so that its axis BB is parallel to a horizontal axis. The spindle 14 may also occupy a dynamic working position, i.e. the head 13 may rotate during a machining operation. In this case the mounting member 21 may be movable and move according to instructions in a machining program and / or the tool post 10 may be movable via the base 12 and move according to instructions in a machining program.

[0044] In a preferred embodiment of the present invention, as shown, the tool post 10 has three main axes 14, 14', and 14". FIG. 2 specifically shows that the main axes 14, 14', and 14" are distributed in the head 13 of the tool post 10, and the main axes 14, 14', and 14" are evenly distributed around the rotation axis of the head 13, i.e., around the axis AA in this embodiment. The main axes 14, 14', and 14" are arranged relative to one another such that, when the axes BB, B-B', and BB" are projected onto a plane P perpendicular to the axis AA, they form an n-th degree regular polygon centered on the axis AA, where n is the number of main axes. In the example shown in FIG. 2, the longitudinal axes of the main axes 14, 14', and 14" form an equilateral triangle.

[0045] Furthermore, in a preferred embodiment of the present invention, the spindles 14, 14' and 14" are arranged such that the axes BB, B-B' and BB" are spaced from the axis AA by a distance greater than the radius of the spindle 14, 14' or 14", for example, a distance at least equal to the diameter of the spindle 14, 14' or 14". This arrangement maximizes the clearance of the cutting tool 15' or 15" from the spindles 14' and 14" in their parked position, thereby avoiding the risk of collision between the cutting tool 15' and 15" and the mounting member 21 or the workpiece. It should be noted that, in general, the more spindles a head has, the greater the distance that the axis AA will be spaced from the spindle axes BB, B-B' and BB".

[0046] Furthermore, as shown particularly in Figure 3, tool post 10 is configured such that axis AA forms an angle of 35 to 55 degrees, preferably 45 degrees, with respect to the vertical axis due to the shape of base 12. Spindles 14, 14' and 14" are therefore disposed in head 13 such that axes BB, B-B' and BB" are inclined at an angle of 35 to 55 degrees, preferably 45 degrees, with respect to axis AA, so that in the working position, the spindles are parallel to the vertical axis as previously described.

[0047] Taken together, as can be derived from the above and from the drawings, the main shafts 14, 14' and 14" are arranged symmetrically with respect to one another along the axis AA, and the axes BB, BB' and BB" of the main shafts 14, 14' and 14" do not intersect with one another.

[0048] Furthermore, a particular arrangement of the spindles 14, 14' and 14" relative to the head 13 of the tool post 10 makes it possible to reduce force loops. In fact, the spindles 14, 14' and 14" are fixed as close as possible to connecting elements formed, for example, by ball bearings, allowing the head 13 to rotate relative to the body 11 of the tool post 10.

[0049] Furthermore, the machine tool 20 may have two tool posts 10 disposed on either side of the mounting member 21, as shown in Figure 4. As shown in this figure, the presence of two tool posts 10 allows two machining operations to be performed simultaneously on the same workpiece. Advantageously, the rotation axes of the spindles 14 of the tool posts 10 in their working positions may be coincident.

[0050] The mounting member 21 may be in the form of a table designed to hold a workpiece in place, with varying degrees of translational and rotational mobility.

[0051] As shown in Figure 4, the machine tool 20 may have a protective wall 23 for protection against splashes of chips and cutting fluid. In particular, the protective wall 23 is arranged in a liquid-tight manner around the body 11 of the or each tool post 10 and has an opening into which said body 11 engages for this purpose. This opening may include a wiper seal at its periphery and arranged against said body 11. Furthermore, the protective wall 23 may advantageously include a bellows. The wiper seal and the bellows allow the tool post to maintain a liquid-tight seal during movement within the XYZ trihedron.

[0052] The protective wall 23 has its peripheral edge fixed to the frame 22 of the machine tool 20 .

[0053] Furthermore, each protective wall 23 advantageously extends in a plane perpendicular to the axis AA, i.e. inclined relative to the horizontal axis, thereby encouraging the flow of cutting fluid and swarf. This arrangement also facilitates operator access to the mounting member 21 and the spindle 14, 14' or 14".

[0054] It should also be noted generally that the implementations and manufacturing methods discussed above have been described as non-limiting examples, and that other variations are therefore possible. [Explanation of symbols]

[0055] 10 Tool rest 11 Main unit 12 Base 13 heads 14, 14', 14” spindle 15, 15', 15” cutting tools 20. Numerical Control Machine Tools 21 Mounting material 22 frames 23 Protective Wall AA axis BB, B-B', BB" longitudinal axis P plane

Claims

1. A tool rest (10) having a body (11) extending along an axis A-A, a base (12) at one end of said body for fixing to a numerically controlled machine tool (20), and a rotatable head (13) at the other end, said head (13) having at least two tool holder spindles (14, 14', 14"), each spindle intended to engage and receive a cutting tool (15, 15', 15"), said tool rest (10) being and each of the spindles (14, 14', 14") is adapted to be controlled independently of the other spindles in order to stop or rotate the cutting tool (15, 15', 15") held therein, regardless of the position it occupies, and The axis of rotation of said head (13) coincides with said axis A-A, the base (12) is configured such that the axis A-A forms an angle of 35 to 55 degrees with respect to a vertical axis; The tool rest (10) is characterized in that each of the spindles (14, 14', 14") has its own motor for rotating or stopping the cutting tool (15, 15', 15") held therein.

2. 2. The tool post (10) according to claim 1, wherein the main axes (14, 14', 14") are three main axes (14, 14', 14") distributed around the rotation axis of the head (13), and the main axes (14, 14', 14") are arranged such that axes B-B, B-B' and B-B" form angles of 35 to 55 degrees with respect to the axis A-A, and such that the axes B-B, B-B' and B-B" do not intersect with each other.

3. 3. The tool post (10) according to claim 2, wherein the main axes (14, 14', 14") are disposed relative to one another such that, when the axes B-B, B-B', and B-B" are projected onto a plane P perpendicular to the axis A-A, they form an equilateral triangle centered on the axis A-A.

4. 3. The tool post (10) according to claim 2, wherein the main spindle (14, 14', 14") is disposed such that the axes B-B, B-B', and B-B" are spaced from the axis A-A by a distance longer than a radius of the main spindle (14, 14', 14").

5. 2. The tool rest (10) of claim 1, wherein at least one spindle (14, 14', 14") is adapted to occupy at least two different working positions, each working position being determined by a predetermined angular position of the head (13) of the tool rest (10).

6. The head (13) moves the spindle (14) that was in the working position to the standby position, and rotates to move the spindle (14') that was in the standby position to the working position; 2. The tool rest (10) of claim 1, wherein at least one spindle (14, 14', 14") is adapted to continuously occupy the working position during rotation of the head (13) of the tool rest (10).

7. A tool rest (10) having a body (11) extending along an axis A-A, a base (12) at one end of said body for fixing to a numerically controlled machine tool (20), and a rotatable head (13) at the other end, said head (13) having at least two tool holder spindles (14, 14', "14"), each spindle intended to engage and receive a cutting tool (15, 15', 15"), said tool rest (10) being adapted to rotate said spindles (14, 14") and to rotate said tool holders (14, 14"), each spindle intended to engage and receive a cutting tool (15, 15', 15"). and each of the spindles (14, 14', 14") is adapted to occupy, depending on the angular position of the head (13), a working position intended to perform a machining operation on a workpiece held in a fixed position on the mounting member (21) or a standby position remote from said workpiece, and each of the spindles (14, 14', 14") is adapted to be controlled independently of the other spindles in order to stop or rotate the cutting tool (15, 15', 15") held therein, regardless of the position it occupies, the main axes (14, 14', 14") are three main axes (14, 14', 14") distributed around the rotation axis of the head (13), and the main axes (14, 14', 14") are arranged such that the axes B-B, B-B' and B-B" form angles of 35 to 55 degrees with the axis A-A, and such that the axes B-B, B-B' and B-B" do not intersect with each other; The tool rest (10) is characterized in that each of the spindles (14, 14', 14") has its own motor for rotating or stopping the cutting tool (15, 15', 15") held therein.

8. A numerically controlled machine tool for machining micromechanical workpieces, comprising at least one tool post (10) according to claim 1, fixed by said base (12) directly to a frame (22) or to a carriage capable of translational movement along an XYZ trihedron; The base (12) of the tool rest (10) is configured such that the axis A-A forms an angle of 35 to 55 degrees with respect to a vertical axis, and the numerically controlled machine tool further includes a workpiece mounting member intended to hold a workpiece to be machined in a fixed position.

9. 9. The numerically controlled machine tool (20) according to claim 8, comprising two tool rests (10) disposed on either side of the workpiece mounting member.

10. 9. A numerically controlled machine tool (20) according to claim 8, comprising a protective wall (23) against splashes of chips and cutting fluid, the body (11) of the or each tool post (10) being fluid-tightly engaged with a corresponding opening in the protective wall (23).

11. 9. A method for changing a cutting tool of a numerically controlled machine tool (20) according to claim 8, comprising the steps of: a first cutting tool (15), engaged with the spindle (14) in a working position, is intended to perform a first machining step, and a second cutting tool (15'), engaged with the spindle (14') in a standby position, is intended to perform a second machining step and is prevented from rotating; - before the end of the first machining stage, the second cutting tool (15') rotates about the B-B' axis until it reaches a rotational speed characteristic of the second machining stage; - when the first machining stage is completed, the head rotates about the axis A-A to drive the spindle (14') holding the second cutting tool (15') to a working position so that the second cutting tool begins the second machining stage, and to drive the spindle (14) holding the first cutting tool (15) to a standby position, the first cutting tool being prevented from rotating when the spindle (14) holding the first cutting tool reaches its standby position.

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